COVID-19 Vaccine Protection Lasts at Least Six Months After Second Dose

TUESDAY, Feb. 7, 2023 (HealthDay News) -- Vaccine protection against severe outcomes from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) lasts at least six months after the second dose, but protection is lower for older patients, according to a study published online Feb. 3 in JAMA Network Open.

Yuchen Wei, Ph.D., from the Chinese University of Hong Kong, and colleagues examined the change in vaccine effectiveness against hospitalization and mortality due to the omicron variant in a case-control study involving adults with SARS-CoV-2 omicron variant infection who died or were hospitalized from Jan. 1 to June 5, 2022 (32,823 case participants) and propensity score-matched adults with SARS-CoV-2 omicron (131,328 control participants).

The researchers found that for at least six months after the second dose of both the CoronaVac and BNT162b2 vaccines, vaccine effectiveness against death or hospitalization was maintained (74.0 and 77.4 percent, respectively). In those aged 18 to 49 years, vaccine effectiveness against death was 86.4 and 92.9 percent for those receiving two doses of CoronaVac and BNT162b2, respectively, while for patients aged 80 years and older, vaccine effectiveness decreased to 61.4 and 52.7 percent, respectively. At four to six months after the third dose, overall vaccine effectiveness against death was >90 percent for CoronaVac, BNT162b2, and the mixed vaccine schedule.

"A booster dose is recommended for older individuals to restore immunity," the authors write. "This is especially critical in a setting like Hong Kong, where coverage of the third dose of the vaccine is still insufficient among older residents."

One author disclosed financial ties to Beth Bioinformatics.

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